The trend in semiconductor fabrication technologies is to minimize the size of semi-conductor devices. Photolithography is a critical step in semiconductor fabrication to control the size of semiconductor devices. However, during the photolithography process, the formation of node patterns for semiconductor devices is often nonuniform due to a well-known phenomenon commonly referred to as the optical proximity effect. The optical proximity effect causes nonuniformity in critical dimensions.
As shown in FIG. 1, to address optical proximity effects and increase areas exposed during lithography, a plurality of serifs 10 are arranged at comers of node patterns 101a, b, c, d. The provision of serifs 10, to some extent, can reduce the distortion caused by the node patterns 101a, b, c, d. However, it will be appreciated that the light intensity caused by exposure is very large in a region designated. Such exposure strongly causes nearby distortion. In addition, such exposure also causes top loss of photoresist during defocus, and reduces the process latitude due to node patterns asymmetries and nonuniform exposure intensities applied to photoresist layers.